1. Field of the Invention
The invention relates to an anchor bolt having a spring, with spring being used to fix various mechanical parts, pipings or the like on a concrete structure such as wall, ceiling, floor or the like.
2. Description of Prior Art
An anchor bolt of the type mentioned above most widely a threaded rod, an expansion body formed at one end of the threaded rod as an anchor body, and an expansion sleeve fitted on the threaded rod penetrating therethrough wherein the expansion sleeve is expanded by the expansion body so as to hold the anchor bolt in a hole of, for example, concrete structure above.
Although the known anchor bolt is advantageous due to its simple structure and is easy to handle in construction work a violent vibration or an earthquake is likely to cause some problems to the anchor bolt. More particularly, the vibration or earthquake causes some cracks on the wall defining the hole, thereby removing the anchor bolt from the hole or gradually moving the bolt outwardly. There are also known some other anchor bolts, for example, disclosed in Japanese Tokkai Publication No. 63-285310 or in U.S. Pat. No. 4,613,264, which comprise a spring member employed to solve the problem mentioned above, with the spring member being interposed between the expansion body and a stopper formed on the threaded rod of anchor body so that a force outwardly pulling the threaded rod acts on the expansion body by the spring member and expands the expansion sleeve.
It is to be noted that in the known anchor bolts comprising the spring member any satisfactory force in axial direction effective to expand the expansion sleeve is not obtained unless the pulling force acting on the threaded rod does completely compresses the spring member, or until the expansion body bears against the stopper. Consequently, an extractable length of the threaded rod is to be increased to ensure the satisfactory force in axial direction. This requirement inevitably increases the length of the threaded rod at its unextracted state, thus making cumbersome the tightening of a nut which mates with the screw rod. Further, the known anchor bolt comprising the spring member are composed of more parts than the first-mentioned known anchor bolt is, causing a higher manufacturing cost. A still further disadvantage in construction work is that the hole must be drilled deeper into the concrete structure.